The present invention relates to electrical machines and apparatus. More specifically, the present invention relates to electrical machines having first and second assemblies movable around more than one axis relative to each other and to apparatus in which such an electrical machine is combined with a circuit for adjusting a set of electrical currents for controlling the machine.
Bers U.S. Pat. No. 3,178,600 shows a structure having continuous helical coils with turns wound on concentric spherical members of high magnetic permeability. Rotation is permitted around just one axis.
Ormsby U.S. Pat. No. 3,260,475 shows a space vehicle directing apparatus with a hollow stainless steel rotor ball suspended in the vehicle by high electric fields. Magnetic fields are applied to induce a current in the rotor ball to magnetically effect a torque on it. An equal and opposite reaction torque turns the vehicle in space. Six substantially semicircular stator coil windings with wires interwound in a core of magnetic material are fixed to a housing and placed about the rotor ball in three mutually perpendicular planes.
F.C. Williams et al. "Development and Design of Spherical Induction Motors," Inst. Electrical Engineers Proceedings, Vol. 106, Part "A", pp. 471-484, Dec. 1959, describes motors with two or four stator blocks wound with a polyphase winding to produce a field travelling across the block. The inside surface of the block is part of a sphere which is concentric with the spherical surface of a rotor which can carry current in any surface direction. By rotating the stator block(s) the speed of the rotor can be varied.
G. Kaminski et al. "Magnetic Field, Parameters and Characteristics of Composite Motion Electric Motor" International Conference on Electric Machines, Budapest, 1982, pp. 335-338 shows spherical motors said to have two or three degrees of freedom. There is a hollow iron ball armature with a smooth surface of copper and chrome. One magnetic circuit of an "inductor" (separated from the ball by an air gap) is said to have two groups of slots in which are located two windings, which produce components of magnetic field perpendicular to each other.
It is believed that the foregoing devices need to be improved for more stable positioning and effective orientation sensing and for other purposes in a variety of fields including prosthetics, electric control systems, and robotics.